Apparatus and method for reducing stray light in substrate processing chambers

ABSTRACT

A method and apparatus for heating semiconductor wafers in thermal processing chambers. The apparatus includes a non-contact temperature measurement system that utilizes radiation sensing devices, such as pyrometers, to determine the temperature of the wafer during processing. The radiation sensing devices determine the temperature of the wafer by monitoring the amount of radiation being emitted by the wafer at a particular wavelength. In accordance with the present invention, a spectral filter is included in the apparatus for filtering light being emitted by lamps used to heat the wafer at the wavelength at which the radiation sensing devices operate. The spectral filter includes a light absorbing agent such as a rare earth element, an oxide of a rare earth element, a light absorbing dye, a metal, or a semiconductor material.

BACKGROUND OF THE INVENTION

A thermal processing chamber refers to a device that uses energy, suchas radiative energy, to heat objects, such as semiconductor wafers. Suchdevices typically include a substrate holder for holding a semiconductorwafer and a light source that emits light energy for heating the wafer.For monitoring the temperature of the semiconductor wafer during heattreatment, thermal processing chambers also typically include radiationsensing devices, such as pyrometers, that sense the radiation beingemitted by the semiconductor wafer at a selected wavelength. By sensingthe thermal radiation being emitted by the wafer, the temperature of thewafer can be calculated with reasonable accuracy.

One major problem in the design of rapid thermal processing chambershaving an optical temperature measurement system, however, has been theability to prevent unwanted light radiated by the heater lamps frombeing detected by the pyrometric instrumentation. Should unwanted lightnot being emitted by the semiconductor wafer be detected by thepyrometer, the calculated temperature of the wafer may unreasonablydeviate from the actual or true temperature of the wafer.

In the past, various methods have been used to prevent unwanted thermalradiation from being detected by the pyrometer. For instance, physicalbarriers have been used before to isolate and prevent unwanted lightbeing emitted by the heater lamps from coming into contact with thepyrometer. Physical barriers have been especially used in rapid thermalprocessing chambers in which the heater lamps are positioned on one sideof the semiconductor wafer and the pyrometer is positioned on theopposite side of the wafer.

Physical barriers, however, can restrict the system design. Forinstance, the physical barrier can restrict how the wafer is supported.In one embodiment, a light-tight enclosure is created below the waferusing a large diameter continuous support ring to hold the wafer at itedges. When a support ring is present, there can be overlap between thesupport ring and the edges of the wafer, which can lead to temperaturenon-uniformities in the wafer during heating cycles. Another problem canarise if the support ring or the wafer is warped even slightly. Whenthis occurs, light can stray through the gap into the supposedlylight-tight region. The stray light can induce errors in the pyrometerreadings.

Besides physical barriers, spectral filters have also been used to limitthe amount of light interference detected by the pyrometers. Forinstance, spectral filters can operate by removing light being emittedby the heater lamps at the wavelength at which the pyrometer operates.Preferably, spectral filters absorb unwanted thermal radiation while atthe same time being transparent to the thermal radiation being emittedby the heater lamps that is necessary to heat the semiconductor wafer.

One type of spectral filter that has been used in the past is a windowmade from fused silica, such as silica doped with hydroxy (OH) ions.Fused silica glass is transparent to most light energy but is known tohave several strong absorbing regions that are maximized at wavelengthsof about 2.7 microns, 4.5 microns and at wavelengths equal to andgreater than 5 microns.

Because certain OH-doped silica glass can effectively absorb light atwavelengths of 2.7, 4.5 and greater than 5 microns and is substantiallytransparent at many other smaller wavelengths of light, silica glassmakes an effective spectral filter when the pyrometer contained withinthe thermal processing chamber is configured to sense thermal radiationat one of the above wavelengths.

Silica glass, however, is unfortunately not well suited to being used asa spectral filter in temperature measurement systems that containpyrometers that sense thermal radiation at shorter wavelengths, such asless than about one micron. Specifically, in some applications, it ismore advantageous and beneficial to operate pyrometers at relativelyshort wavelengths. In particular, by using pyrometers that operate atshorter wavelengths, the effects of wafer emissivity variations can beminimized providing for more accurate temperature determinations.Specifically, at lower wavelengths, silicon wafers are more opaque andthe emissivity of the wafer is not significantly temperature dependent.The emissivity of the wafer is one variable that must be known with someaccuracy in determining the temperature of wafers using pyrometers.

In addition to more precisely determining the temperature of wafers,pyrometers that operate at relatively shorter wavelengths are alsogenerally less expensive and less complicated then pyrometers that areconfigured to operate at higher wavelengths. Further, pyrometers thatsense thermal radiation at lower wavelengths generally operate veryefficiently and can generate low noise measurements.

In the past, however, pyrometers that operate at lower wavelengths havebeen selectively used in thermal processing chambers due to thesignificant amount of stray light that can be detected in thermalprocessing chambers at lower wavelengths. As such, a need currentlyexists for a spectral filter that can efficiently absorb light energy atlower wavelengths, such as wavelengths less than about 2 microns.

SUMMARY OF THE INVENTION

The present invention is generally directed to an apparatus and methodfor heat treating semiconductor devices. The apparatus includes athermal processing chamber adapted to contain a semiconductor wafer. Aradiant energy source including at least one lamp is used to emit lightenergy into the chamber. At least one radiation sensing device islocated within the thermal processing chamber and is configured to sensethermal radiation at a preselected wavelength being emitted by asemiconductor wafer being heat treated.

In accordance with the present invention, the apparatus further includesa spectral filter that is configured to absorb thermal radiation beingemitted by the light source at the preselected wavelength at which theradiation sensing device operates. The spectral filter comprises a lightabsorbing agent. The light absorbing agent can be, for instance, a rareearth element, a light absorbing dye, a metal, or a semiconductormaterial. For example, in one embodiment, the spectral filter comprisesa host material doped with a rare earth element. The rare earth elementcan be ytterbium, neodymium, thulium, erbium, holmium, dysprosium,terbium, gadolinium, europium, samarium, praseodymium, or mixturesthereof.

In an alternative embodiment, the spectral filter comprises a hostmaterial doped with a metal, such as a transition metal. Particularmetals that can be used, include, for instance, iron and copper.

The host material can be a liquid, a glass, a crystal, a plastic or aceramic. Of particular advantage, when the spectral filter contains arare earth element, the spectral filter can be configured to absorblight energy at a wavelength of less than about 2 microns, such as fromabout 0.5 microns to about 1.5 microns, and particularly from about 0.6microns to about 1.1 microns. For example, in one embodiment, thespectral filter can be ytterbium contained in a glass material in anamount of at least 0.5% by weight, and particularly in an amount of atleast about 20% by weight. In this embodiment, the spectral filter canbe configured to absorb light at a wavelength of between about 900 nm toabout 1010 nm.

As described above, the amount of the light absorbing agent presentwithin the host material can be measured in units of percentage byweight. For example, for many applications, the light absorbing agentcan be present in the host material in an amount from about 0.5% toabout 50% by weight. In some applications, however, it may be moreappropriate to use atomic composition as a measure of concentrationinstead of weight percentages. For example, the light absorbing agentcan be present in the host material at an atomic compositionconcentration (mole percent) of from about 0.5% to about 50%. The atomiccomposition concentration can vary depending upon the particular hostmaterial and the particular light absorbing agents selected.

In an alternative embodiment, the rare earth element can be in the formof a rare earth element compound, such as an oxide. The rare earthelement compound can be contained in a ceramic material and used as aspectral filter in accordance with the present invention.

As described above, in another embodiment, the light absorbing agent canbe a light absorbing dye. The dye can be, for instance, an organic saltdye, a nickel complex dye, a precious metal dye such as a platinumcomplex dye or a palladium dye, a phalocyanine dye, or an anthraquinoneor a mixture thereof. Such dyes are also well-suited to absorbing lightat wavelengths less than about 2 microns.

In addition to rare earth elements and light absorbing dyes, thespectral filter can also be made from a semiconductor material. Thesemiconductor material can be, for instance, gallium arsenide, aluminumarsenide, germanium, silicon, indium phosphide, or alloys of thesematerials, such as Si/Ge; AlAs/GaAs/InP.

Spectral filters made in accordance with the present invention can havean attenuation factor of at least 5 at the wavelength of interest. Forinstance, the spectral filter can have an attenuation factor of at least10³, and particularly can have an attenuation factor of at least 10⁵ atthe wavelength of interest. Further, the above attenuation factors canbe obtained having a relatively thin material. For instance, thespectral filter can have a thickness of less than about 1 inch, andparticularly less than about 100 mm.

The spectral filter can be positioned in association with the lightsources in the apparatus of the present invention at various locations.For instance, in one embodiment, the spectral filter can be positionedin between the thermal processing chamber and the light sources. In analternative embodiment, however, the spectral filter can be used tosurround a lamp or a radiant energy filament. In still anotheralternative embodiment, the spectral filter can be incorporated into areflector that is positioned behind the light sources.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a cross-sectional view of one embodiment of an apparatus forheat treating semiconductor devices in accordance with the presentinvention;

FIG. 2 is a cross-sectional view of an alternative embodiment of anapparatus for heat treating semiconductor devices in accordance with thepresent invention;

FIG. 3A is a cross-sectional view of one embodiment of a lamp surroundedby a spectral filter in accordance with the present invention;

FIG. 3B is a cross-sectional view of another alternative embodiment of alamp surrounded by a spectral filter in accordance with the presentinvention;

FIG. 4 is a perspective view of a plurality of lamps placed inassociation with one embodiment of a spectral filter made in accordancewith the present invention; and

FIG. 5 is a graph of light transmission versus wavelength for a spectralfilter containing ytterbium in accordance with the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the present inventionwhich broader aspects are embodied in the exemplary construction.

In general, the present invention is directed to an apparatus and methodfor heating semiconductor wafers while accurately monitoring thetemperature of the wafer. The apparatus includes a thermal processingchamber in communication with a light source that is used to heatsemiconductor wafers contained in the chamber. A radiation sensingdevice, such as a pyrometer, is in communication with the chamber and ispositioned to sense thermal radiation at a particular wavelength beingemitted by a semiconductor wafer. By sensing the thermal radiation beingemitted by the wafer at a particular wavelength, the pyrometer can beused to calculate the temperature of the wafer during operation of thethermal processing chamber.

In accordance with the present invention, the apparatus further includesa spectral filter positioned in communication with the light source. Thespectral filter absorbs light energy emitted by the light source at thewavelength at which the radiation sensing device operates in order toprevent the absorbed light from being detected by the radiation sensingdevice and interfering with any temperature measurements being taken.The spectral filter, however, is substantially transparent to lightenergy being emitted by the light source that is needed for heating asemiconductor wafer contained in the chamber.

In accordance with the present invention, various materials can be usedto construct the spectral filter. For example, in one embodiment, thespectral filter can include a host material containing a light absorbingagent. The light absorbing agent can be, for instance, a rare earthelement or a light absorbing dye. Examples of rare earth elements thatcan be used in accordance with the present invention include ytterbium,neodymium, thulium, erbium, holmium, dysprosium, terbium, gadolinium,europium, samarium, praseodymium, and mixtures thereof.

Light absorbing dyes that can be used in accordance with the presentinvention include, organic salt dyes, nickel complex dyes, preciousmetal dyes, such as platinum complex dyes and palladium complex dyes,phalocyanine dyes, anthraquinone dyes, and mixtures thereof.

In alternative embodiments, the spectral filter can be made from acompound containing a rare earth element (such as an oxide) or asemiconductor material. The rare earth element compound can be acompound of any of the rare earth elements described above. Examples ofsemiconductor materials that can be used as a spectral filter includegallium arsenide, aluminum arsenide, indium phosphide, silicon,germanium, or alloys of these materials. When using a semiconductormaterial as a spectral filter, the spectral filter may need to be cooledduring heating of semiconductor wafers contained in the thermalprocessing chamber depending upon the position of the spectral filter.

The present invention provides various benefits and advantages indetermining the temperature of wafers during heating processes. Inparticular, the spectral filter can absorb and eliminate unwantedradiation from being sensed by the radiation sensing device for moreaccurately determining the temperature of the wafers. Of particularadvantage, in one embodiment, a spectral filter made in accordance withthe present invention can be chosen that is very efficient at absorbinglight at relatively short wavelengths, such as wavelengths less thanabout 2 microns, and particularly at wavelengths less than about 1micron. In other embodiments, however, spectral filters made inaccordance with the present invention can be designed to absorb light atwavelengths longer than 2 microns which may be desired in someapplications.

Referring to FIG. 1, an apparatus generally 10 made in accordance withone embodiment of the present invention for processing semiconductordevices, such as silicon wafers, is shown. Apparatus 10 includes aprocessing chamber 12 adapted to receive substrates such as asemiconductor wafer 14 for conducting various processes. Chamber 12 isdesigned to heat wafer 14 at rapid rates and under carefully controlledconditions. Chamber 12 can be made from various materials, includingmetals and ceramics. For instance, chamber 12, in one embodiment, can bemade from stainless steel.

When chamber 12 is made from a heat conductive material, the chamber caninclude a cooling system. For instance, as shown in FIG. 1, chamber 12includes a cooling conduit 16 wrapped around the perimeter of thechamber. Conduit 16 is adapted to circulate a cooling fluid, such aswater, which is used to maintain the walls of chamber 12 at a constanttemperature.

Chamber 12 can also include a gas inlet 18 and a gas outlet 20 forintroducing a gas into the chamber and/or for maintaining the chamberwithin a preset pressure range. For instance, a gas can be introducedinto chamber 12 through gas inlet 18 for reaction with wafer 14. Onceprocessed, the gas can then be evacuated from the chamber using gasoutlet 20.

Alternatively, an inert gas can be fed to chamber 12 through gas inlet18 for preventing any unwanted or undesirable side reactions fromoccurring within the chamber. In a further embodiment, gas inlet 18 andgas outlet 20 can be used to pressurize chamber 12. A vacuum can also becreated in chamber 12 when desired, using gas outlet 20 or an additionallarger outlet positioned beneath the level of the wafer.

During processing, chamber 12, in one embodiment, can be adapted torotate wafer 14. Rotating the wafer promotes greater temperatureuniformity over the surface of the wafer and promotes enhanced contactbetween wafer 14 and any gases introduced into the chamber. It should beunderstood, however, that besides wafers, chamber 12 is also adapted toprocess optical parts, films, fibers, ribbons and other substrateshaving any particular shape.

A light source generally 22 is included in communication with chamber 12for emitting light energy and heating wafer 14 during processing. Inthis embodiment, light source 22 includes a plurality of lamps 24. Lamps24 can be incandescent lamps, such as tungsten-halogen lamps, arc lamps,or the like. Light source 22 can include a reflector or a set ofreflectors for carefully directing light energy being emitted by lamps24 uniformly onto wafer 14. As shown in FIG. 1, lamps 24 are placedabove wafer 14. It should be understood, however, that lamps 24 may beplaced at any particular location. Further, additional or less lampscould be included within apparatus 10 as desired.

In some thermal processing apparatuses, the use of lamps 24 as a heatsource is preferred. For instance, lamps have much higher heating andcooling rates than other heating devices. Lamps 24 create a rapidthermal processing system that provides instantaneous energy, typicallyrequiring a very short and well controlled start up period. The flow ofenergy from lamps 24 can also be abruptly stopped at any time. The lampscan be equipped with gradual power controls and can be connected to acontroller that automatically adjusts the amount of light energy beingemitted by the lamps based on temperature measurements of the wafer.

In addition to lamps 24, however, the apparatus 10 can also include asusceptor positioned within the thermal processing chamber 12 at alocation adjacent to the wafer 14. The susceptor can include a heatingelement, such as an electrical resistance heater or an induction heaterfor heating the wafer in addition to the lamps.

Semiconductor wafer 14 is supported within thermal processing chamber 12by a substrate holder 26. Substrate holder 26, in this embodiment, alsosupports a plurality of optical fibers or light pipes 28 which are, inturn, in communication with a radiation sensing device(s) 30, such as apyrometer(s). Alternatively to the embodiment illustrated in FIG. 1,each optical fiber 28 can be connected to a separate radiation sensingdevice if desired.

In a further embodiment, the use of optical fibers may not be necessaryin order to transmit radiant energy to the pyrometers. For example,simple lens systems can be used instead of optical fibers. Further, inother embodiments, the pyrometers can be placed in a direct line ofsight with the substrate being processed. The particular arrangement ofthe temperature measurement device in the apparatus of the presentinvention depends on the configuration and the particular application.

Optical fibers 28 are configured to receive thermal radiation beingemitted by wafer 14 at a particular wavelength. The amount of sensedradiation is then communicated to radiation sensing device 30 whichgenerates a usable voltage signal for determining the temperature of thewafer.

In this embodiment, apparatus 10 is designed such that optical fibers 28only detect thermal radiation being emitted by the wafer and do notdetect substantial amounts of radiation being emitted by lamps 24. Inthis regard, apparatus 10 includes a spectral filter 32 positionedbetween light source 22 and radiation sensing device 30. The spectralfilter substantially prevents thermal radiation being emitted by lamps24 at the wavelength at which radiation sensing device 30 operates fromentering chamber 12.

In accordance with one embodiment of the present invention, the spectralfilter 32 includes a light absorbing agent contained within a hostmaterial. In general, the spectral filter 32, on one hand, preventsthermal radiation being emitted by the lamps 24 at the wavelength atwhich the radiation sensing device 30 operates from entering the chamber12, while, on the other hand, permitting the transmission of radiationat other wavelengths in amounts sufficient to heat the wafer 14.Generally speaking, the spectral filter 32 can be designed according tothe present invention to filter many different wavelengths andwavelength ranges.

In one particular embodiment, the spectral filter 32 is designed tofilter relatively short wavelengths. For example, in the case ofsemiconductor materials, it can be more convenient to use radiationsensing devices that sense at wavelengths below the semiconductorabsorption edge, which corresponds to a photon energy higher than thesemiconductor band gap. At these wavelengths, the sample will generallybe opaque at the measurement wavelength. Consequently, transmission ofthe sample does not vary strongly with temperature and wafer doping, asis usually the case for wavelengths beyond the absorption edge.

At lower wavelengths, Plank's Law used to calculate temperature developsa very strong temperature dependence. Consequently, at smallerwavelengths, very large decreases in signal strength as the temperaturedrops may be experienced. Thus, the lowest temperature that can bereliably measured in a thermal processing chamber will usually belimited either by noise in the detection system or by stray light thatcannot be distinguished from wafer signal. As a result, the ratio ofwafer radiation to stray light tends to improve as the detectionwavelength increases. Consequently, in some embodiments, relativelyaccurate results are obtained when the temperature measurement devicesoperate at a wavelength of from about 0.5 microns to about 1.5 microns,and particularly from about 0.8 microns to about 1.1 microns. Spectralfilters made in accordance with the present invention can be designed tofilter wavelengths within the above ranges.

As described above, in one embodiment, the spectral filter 32 includes alight absorbing agent contained within a host material. In accordancewith the present invention, the light absorbing agent can be, forinstance, a rare earth element or a light absorbing dye. The hostmaterial for the light absorbing agent can be, for instance, glass,ceramics, crystals, and the like.

Once constructed, the spectral filter should be capable of effectivelyfiltering thermal radiation at the wavelength of interest, which is thewavelength at which the radiation sensing device operates. In thisregard, the absorption coefficient of the spectral filter has to be highenough to provide the desired attenuation of radiation at the wavelengthof interest. For example, for most applications, the spectral filtershould have an attenuation factor of at least 5, particularly at least100, and more particularly at least 1000. For example, in oneembodiment, the attenuation factor can be greater than about 10⁹. Asused herein, the attenuation factor is calculated as follows:attenuation factor=exp (−αd),wherein alpha is the absorption coefficient (1/cm) and d is thethickness (cm) of the spectral filter.

The absorption coefficient and the thickness of the spectral filer canvary as long as the attenuation factor falls within a useful range atthe wavelength of interest. For most applications, however, the materialshould have an absorption coefficient greater than about 5 cm⁻¹,particularly greater than about 10 cm⁻¹, and more particularly greaterthan about 50 cm⁻¹. In general, the spectral filter should be as thin aspossible. For example, the spectral filter should have a thickness ofless than about 100 mm, particularly less than 25 mm and in oneembodiment can have a thickness of less than about 5 mm. It should beunderstood, however that the thickness of the spectral filter can beincreased above the above ranges in order to provide a desiredattenuation factor.

The various light absorbing agents and host materials that can be usedin the present invention will now be described in more detail. Forexample, as stated above, in one embodiment, the light absorbing agentincludes a rare earth element. Rare earth elements that can be used inthe present invention include ytterbium, neodymium, thulium, erbium,holmium, dysprosium, terbium, gadolinium, europium, samarium,praseodymium, and the like.

For instance, ytterbium has been found to have a strong absorption peakbetween about 900 nm to about 1010 nm, and particularly between about950 nm and 985 nm. The wavelengths that are absorbed by ytterbium,however, may be slightly affected by the host material. Erbium andneodymium also have been found to have strong absorption peaks atwavelengths less than about 1.5 microns and greater than about 0.6microns.

As described above, however, the spectral filters made according to thepresent invention can also be used to absorb wavelengths greater thanabout 1.5 microns. For example, holmium, europium and terbium have beenfound to have good absorption characteristics for wavelengths from about1.7 microns to about 2.4 microns. More particularly, holmium has anabsorption peak at 1.49 microns, europium has an absorption peak atabout 2.09 microns, and terbium has an absorption peak of between about1.85 microns and about 2.1 microns.

In order to illustrate the absorption characteristics of rare earthelements, included as FIG. 5 is a graph of light transmission versuswavelength for a glass doped with ytterbium. The glass was obtained fromthe Schott Company and was sold under the designation Schott S-8050Glass. The glass had a thickness of about 14 mm and contained about 30%by weight of ytterbium. As shown, in this embodiment, the glass dopedwith ytterbium is well-suited for absorbing light in a wavelength rangeof from about 900 nm to about 980 nm, and is particularly well-suitedfor absorbing light having a wavelength of from about 940 nm to about980 nm.

As stated above, in addition to glass, the host material for the rareearth element can be a ceramic or a crystalline or a plastic material.In general, any suitable host material can be used, including liquidmaterials. For most applications, it is preferred that the lightabsorbing agent have a high solubility in the host material. Further,preferably the host materials are low cost, and can be easily formedinto desired shapes. Further, preferably the host material is alsoresistant to chemical attack when directly exposed in the processchamber.

The amount of the light absorbing agent incorporated into the hostmaterial will depend upon the particular application and desiredresults. For most applications, however the host material should containthe light absorbing agent in an amount of at least 0.5% by weight,particularly at least 10% by weight, and more particularly at least 20%by weight. For instance, in one embodiment, the host material cancontain the light absorbing agent in an amount from about 0.5% by weightto about 50% by weight. As described above, in some applications, theamount of the light absorbing agent in the host material can also beexpressed in atomic composition concentration.

The following are various materials that can be used as host materialsin accordance with the present invention. It should be understood,however, that the following list is merely exemplary and is notexhaustive.

Glass Materials

-   -   Silica, SiO₂    -   Germanium oxide GeO₂    -   Titanium dioxide TiO₂    -   Silicate glasses (Li-silicate, Na-silicate)    -   Silicate glass: (Nb₂O₅—ZrO₂—SiO₂)    -   Silicate glass: Schott LG-680 (laser glass)    -   Silicate glass: Kigre Q-246    -   Aluminosilicate glass    -   Aluminogermanosilicate glass    -   Borosilicate glass    -   Germanosilicate glasses    -   Phosphate glasses    -   Phosphate glass: (BaO—K₂O—P₂O₅)    -   Phosphate glass Schott LG-700, LG-750, LG-760 (laser glasses)    -   QX (Kigre),ADY,LY,PN, PNK phosphate glasses    -   NASICON phosphate glass Na₄AlZnP₃O₁₂    -   Fluorophosphate glasses    -   Fluoride phosphate glass    -   Fluoride sulphate glass    -   Fluoroaluminate glass    -   Germanate glasses (K-Germanate)    -   Chalcogenide glasses    -   Gallium Lanthanum sulphide glasses—chalcogenide    -   Halide glasses    -   Heavy metal fluoride glasses    -   ZB, ZBLA, ZBLAN & ZBLANP        (ZBLANP═ZrF₄—BaF₂—LaF₃—AlF₃—NaF—PbF₂)-heavy-metal fluoride        glasses    -   Fluorozirconate glasses    -   BIGaZYT    -   Fluoroborate glasses    -   Lead fluoroborate glasses (PbO—PbF₂—B₂O₃)    -   Lead oxyfluoride glasses (PbO—PbF₂)    -   Lead borate glasses (PbO—B₂O₃)    -   Lead fluoroborate glass (PbO—PbF₂—B₂O₃)    -   Tellurite glasses (YTG)    -   Tellurite glass (TeO2-ZnO—Na₂O)    -   Telluride glasses

Crystalline Materials

-   -   Yttrium Aluminium Garnet (YAG=Y₃Al₅O₁₂)    -   Sapphire Al₂O₃    -   Y₂O₃, Sc₂O₃, Lu₂O₃ (sesquioxides)    -   Semiconductor crystals (AlAs, GaAs, GaP, InP, AlGaAs, CdTe, CdS,    -   CdSe, ZnS, ZnSe, ZnTe, SiC, Si)    -   LaBr₃, LaCl₃, LaF₃, LiYF₄, YAlO₃, YVO₄    -   Sr₃Y(BO₃)₃(BOYS)    -   Ca₄Gd(BO₃)₃O(GdCOB)    -   Ca₄Y(BO₃)₃O(YCOB)    -   KGd(WO₄)₂    -   KY(WO₄)₂    -   Sr₅(PO₄)₃F(S—FAP)—apatite structure    -   Ca₅(PO₄)3_(F)(C—FAP)—apatite structure    -   Ba₅(PO₄)₃F    -   LiNbO₃    -   Ca₈La₂(PO₄)₆O₂(CLYPA)—oxoapatite

Ceramic Materials

-   -   Alumina (Al₂O₃)    -   Aluminium Oxynitride (sometimes called AlON)    -   Ceramic forms of YAG    -   Silicon carbide    -   Silicon nitride    -   Spinel

Instead of a rare earth element, in one embodiment, the light absorbingagent can be a metal, such as a transition metal. For example, inparticular embodiments, iron or copper can be incorporated into the hostmaterial. In general, these materials can be incorporated into the hostmaterial in the same amounts as expressed above for the rare earthelements.

In additional to the host material containing a rare earth element or ametal, as described above, the light absorbing agent can also be a lightabsorbing dye. The light absorbing dye can be used alone or can be usedin conjunction with rare earth elements and/or the above-describedmetals. The light absorbing dyes described herein can be incorporatedinto various host materials. Some light absorbing dyes, however, may betemperature sensitive. As such, the dyes, in some embodiments, may bebetter suited to be incorporated into plastics and solvents as opposedto some of the other host materials described above.

Many different types of light absorbing dyes can be used in the presentinvention depending upon the desired results. For example, the lightabsorbing dye can be an organic salt dye (Epolin 100 & 2000 series), anickel complex dye (Epolin 3000 series; SDA6370, 845 nm from H. W. SandsCorp.), precious metal dyes such as a platinum complex dye and apalladium complex dye (Epolin 4000 series are platinum and palladiumdyes; SDA5484, 886 nm H.W. Sands corp. is a palladium dye), aphalocyanine dye (Epolin 6000 series) or an anthraquinone dye (Epolin9000 series). The light absorbing dyes can be used alone or incombination with other dyes. The dyes listed above can be optimized bycomputer stimulation before formulation. Further, a light absorbing dyecan also be used in conjunction with a rare earth element.

The light absorbing dyes of the present invention can also be combinedwith various agents and stabilizers prior to or during incorporationinto a host material. For example, thermal stabilizers and lightstabilizers can be added to the dyes. For example, epolin “class V dyes”including EPOLIGHT 4029 have high thermal stability and ultravioletstability. Ultraviolet light stabilizers that can be added to the dyesinclude, for instance, cerium oxide.

Some commercially available light absorbing dyes that can be used in thepresent invention include the following: LIGHT ABSORPTION SUPPLIER NAMEPRODUCT NAME PEAK Epolin, Inc. Epolight 2057 990 nm (Organic salt dye)Epolin, Inc. Epolight 4129 886 nm (Platinum or palladium dye) Epolin,Inc. Epolight 6089 684 nm (phthalocyanine dye) Gentex Corp. Filtron A187840 nm Gentex Corp. Filtron A103 700 nm H. W. Sands Corp. Dye SDA3598738 nm (Precious metal dye) H. W. Sands Corp. Dye SDA3805 798 nm H. W.Sands Corp. Dye SDA7973 845 nm H. W. Sands Corp. Dye SDA909 909 nm H. W.Sands Corp. Dye SDA9510 951 nm (Precious metal dye) H. W. Sands Corp.Dye SDA1168 1046 nm 

In addition to host materials doped with a rare earth element orcontaining a light absorbing dye, various other materials can be used toconstruct a spectral filter in accordance with the present invention.For example, in one embodiment, the spectral filter can be made from anoxide of a rare earth element. For instance, ytterbium oxide (Yb₂O₃) canbe used. The oxides can be used in either a crystalline form, a glassform or a ceramic form. Further the oxides can be mixed together or withother components to form a multi-component ceramic or a glass for use inthe present invention.

In another embodiment, the spectral filter can be made from asemiconductor material. The semiconductor material can be, for instance,gallium arsenide, aluminum arsenide, indium phosphide, silicon,germanium or alloys of these materials. For example gallium arsenide iswell-suited for absorbing light at a wavelength of less than about 0.9microns. When using a semiconductor material, however, it may benecessary to cool the spectral filter during operation of the processingchamber. The spectral filter can be cooled, for instance, by circulatinga cooling fluid throughout or adjacent to the filter material. Thecooling fluid can be for instance, air or water. Of course, any suitablecooling device can be used for this purpose.

The semi-conductor materials can also be coated with an anti-reflectioncoating due to the tendency of some materials to have high-refractiveindices, and consequently tend to reflect a large amount of light.Anti-reflection coatings can be made from, for instance, thin films ofsilicon dioxide or silicon nitride. Multi-layer coatings can also bedesigned and applied to achieve a broadband coating that is effectiveover a wide spectral range. The coatings can be used alone or incombination with various absorbing elements. In one embodiment, theanti-reflective coating can be used that has a high reflectivity at thewavelength at which the pyrometer operates.

Referring to FIG. 2, another embodiment of a thermal processingapparatus generally 10 made in accordance with the present invention isillustrated. Like reference numerals have been included to indicatesimilar elements. As shown, in this embodiment, the wafer 14 is heatedfrom both sides using two sets of light energy sources 24. Thus, in thisembodiment, the apparatus includes a first spectral filter 32 and asecond spectral filter 132, which serve to isolate the wafer from thelamps.

In this embodiment, the spectral filters 32 and 132 include openings forthe optical fibers 28 of the radiation sensing devices 30. The openingsallow radiation being emitted by the wafer to be transmitted to theradiation sensing devices. As shown, the spectral filters 32 and 132filter the light energy being emitted by the lamps 24 into theprocessing chamber 12. In accordance with the present invention, thespectral filters 32 and 132 can be made from any of the materialsdescribed above.

In another embodiment of the present invention, the spectral filter 32can be used to form the lamp housing itself. In particular, the spectralfilter can be placed in direct association with the lamp filament thatproduces radiant energy.

In still another embodiment, the spectral filter of the presentinvention can be applied as a coating to the lamp envelope.

In addition to forming openings in the spectral filters 32 and 132, inan alternative embodiment, the optical fibers 28 or the pyrometer itselfcan be contained in regions where the host material is not doped withthe light absorbing agent. In this manner, the pyrometer has a view portthrough these regions to take measurements from the wafer. In oneembodiment, the regions can be formed by fusing undoped glass piecesinto a doped glass sheet that has been formed with openings.

In addition to placing the optical fibers 28 within the spectralfilters, however, the optical fibers can be placed in other locations aswell. For instance, the optical fibers can also extend completelythrough the filter or through the chamber sidewalls.

In addition to being in the form of windows that isolate the thermalprocessing chamber from the lamps, the spectral filters of the presentinvention can also be constructed in other arrangements. For instance,as shown in FIGS. 3A and 3B, the spectral filter 32 can be in the formof a sleeve that is placed around individual lamps or groups of lamps.As shown in FIG. 3A, the lamp 24 can be vertically oriented orhorizontally oriented as shown in FIG. 3B. In this arrangement, thespectral filters 32 can be used alone or in conjunction with otherwindows that served to isolate the chamber 12.

In another embodiment of the present invention, the optical fibers 28 asshown in FIGS. 1 and 2 can be placed outside of the thermal processingchamber 12 in the same vicinity of the lamps 24. In this arrangement,light emitted by the lamps go through the spectral filter twice prior tobeing detected by the optical fibers. Light being emitted from thewafer, however, only travels through the spectral filter once prior tobeing detected by the optical fiber. Consequently, the ratio of straylight to signal will improve for making accurate temperaturemeasurements.

In still another embodiment of the present invention, the apparatus 10can include a pair of windows in parallel that have a first windowadjacent the lamps and a second window adjacent the chamber. In thismanner, a cooling fluid, such air or water, can be circulated betweenthe two windows. One or both of the windows can be a spectral filter inaccordance with the present invention. When one of the windows is notbeing used as a spectral filter, the window can be made from, forinstance, quartz or sapphire.

Referring to FIG. 4, in another embodiment of the present invention, thespectral filter can be in the form of a reflector 40 placed inassociation with a plurality of lamps 24. For example, the reflector 40can include a first layer 42 and a second layer 44. The first layer 42can be made from a highly reflective material, such a metal. The secondlayer 44, can contain a light absorbing agent in accordance with thepresent invention. In this manner, the second layer 44 serves to filterlight being reflected from the lamps and into the thermal processingchamber. Thus, although direct light emitted by the lamps at thewavelength of interest may reach the chamber, the amount of reflectedlight at the wavelength of interest is reduced. Depending upon theparticular application, the reflector 40 can reduce the amount of lightat the wavelength at which the radiation sensing devices operate in anamount sufficient for relatively accurate temperature measurements to betaken.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only and, is not intended to limit the invention sofurther described in such appended claims.

1-47. (canceled)
 48. An apparatus for heat treating substratescomprising: a thermal processing chamber for receiving a substrate; aradiative energy source in communication with the thermal processingchamber for emitting radiant energy into the chamber; at least oneradiation sensing device in communication with the thermal processingchamber, the radiation sensing device being configured to senseradiation at a preselected wavelength; and a spectral filter beingpositioned in communication with the radiative energy source, thespectral filter being configured to absorb radiation being emitted bythe radiative energy source at the preselected wavelength, the spectralfilter comprising a light absorbing agent, the light absorbing agentcomprising a material selected from the group consisting of a rare earthelement, a dye, a rare earth element oxide, a semiconductor material,and a metal, the spectral filter comprising a sleeve that surrounds theradiative energy source.
 49. An apparatus as defined in claim 48,wherein the radiative energy source comprises a plurality of lamps andwherein the sleeve surrounds all of the lamps.
 50. An apparatus asdefined in claim 48, wherein the radiative energy source comprises aplurality of lamps and wherein the apparatus comprises a correspondingplurality of spectral filters that each surround a corresponding lamp.51. An apparatus as defined in claim 48, wherein the radiative energysource comprises a lamp containing a lamp filament, the spectral filterbeing integral with the lamp and comprising a lamp housing that is indirect association with and encloses the lamp filament.
 52. An apparatusas defined in claim 48, wherein the radiative energy source comprises alamp, the lamp including a lamp filament and a lamp housing, thespectral filter comprising a coating on the lamp housing.
 53. Anapparatus as defined in claim 48, wherein the light absorbing agentcomprises a dye, the dye comprising an organic salt dye, a nickelcomplex dye, a precious metal dye, a phalocyanine dye, or ananthroquinone or mixtures thereof.
 54. An apparatus as defined in claim48, wherein the spectral filter comprises a host material doped with thelight absorbing agent, the light absorbing agent comprising a rare earthelement, the rare earth element being a material selected from the groupconsisting of ytterbium, neodymium, thulium, erbium, holmium,dysprosium, terbium, gadolinium, europium, samarium, praseodymium, andmixtures thereof.
 55. An apparatus as defined in claim 48, wherein thepredetermined wavelength is less than about 1.5 microns.
 56. Anapparatus as defined in claim 48, wherein the spectral filter has anattenuation factor of at least 10³.
 57. An apparatus as defined in claim48, wherein the light absorbing agent comprises a metal, the metalcomprising iron or copper.
 58. An apparatus as defined in claim 48,wherein the light absorbing agent comprises a semiconductor material,the semiconductor material comprising gallium arsenide, aluminumarsenide, silicon, germanium, indium phosphide or alloys thereof.
 59. Anapparatus for heat treating substrates comprising: a thermal processingchamber for receiving a substrate; a radiative energy source incommunication with the thermal processing chamber for emitting radiantenergy into the chamber; at least one radiation sensing device incommunication with the thermal processing chamber, the radiation sensingdevice being configured to sense radiation at a preselected wavelength;and a first window spaced from a second window, the first and secondwindows being positioned in between the radiative energy source and theat least one radiation sensing device, the first window comprising aspectral filter, the spectral filter being configured to absorbradiation being emitted by the radiative energy source at thepreselected wavelength, the spectral filter comprising a light absorbingagent, the light absorbing agent comprising a rare earth element or adye.
 60. An apparatus as defined in claim 48, further comprising acooling fluid source for circulating a cooling fluid in between thefirst window and the second window.
 61. An apparatus as defined in claim59, wherein the spectral filter is positioned in between the radiativeenergy source and the second window.
 62. An apparatus as defined inclaim 59, wherein the spectral filter is positioned in between thesecond window and the at least one radiation sensing device.
 63. Anapparatus as defined in claim 59, wherein the light absorbing agentcomprises a dye, the dye comprising an organic salt dye, a nickelcomplex dye, a precious metal dye, a phalocyanine dye, or ananthroquinone or mixtures thereof.
 64. An apparatus as defined in claim59, wherein the spectral filter comprises a host material doped with thelight absorbing agent, the light absorbing agent comprising a rare earthelement, the rare earth element being a material selected from the groupconsisting of ytterbium, neodymium, thulium, erbium, holmium,dysprosium, terbium, gadolinium, europium, samarium, praseodymium, andmixtures thereof.
 65. An apparatus for heat treating substratescomprising: a thermal processing chamber for receiving a substrate; aradiative energy source in communication with the thermal processingchamber for emitting radiant energy into the chamber; at least oneradiation sensing device in communication with the thermal processingchamber, the radiation sensing device being configured to senseradiation at a preselected wavelength; and a reflector placed inassociation with the radiative energy source, the reflector comprising aspectral filter configured to absorb radiation being emitted by theradiative energy source at the preselected wavelength, the spectralfilter comprising a light absorbing agent, the light absorbing agentcomprising a material selected from the group consisting of a rare earthelement, a dye, a rare earth element oxide, a semiconductor material,and a metal.
 66. An apparatus as defined in claim 65, wherein thereflector includes a first layer and a second layer, the first layercomprising a highly reflective material, the second layer comprising thespectral filter, the second layer covering the first layer.
 67. Anapparatus as defined in claim 65, wherein the spectral filter comprisesa host material doped with the light absorbing agent, the lightabsorbing agent comprising a rare earth element, the rare earth elementbeing a material selected from the group consisting of ytterbium,neodymium, thulium, erbium, holmium, dysprosium, terbium, gadolinium,europium, samarium, praseodymium, and mixtures thereof.
 68. An apparatusas defined in claim 65, wherein the light absorbing agent comprises adye, the dye comprising an organic salt dye, a nickel complex dye, aprecious metal dye, a phalocyanine dye, or an anthroquinone or mixturesthereof.
 69. An apparatus for heat treating substrates comprising: athermal processing chamber for receiving a substrate; a radiative energysource in communication with the thermal processing chamber for emittingradiant energy into the chamber; at least one radiation sensing devicein communication with the thermal processing chamber, the radiationsensing device being configured to sense radiation at a preselectedwavelength; and a spectral filter being positioned in between theradiative energy source and the at least one radiation sensing device,the spectral filter being configured to absorb radiation being emittedby the radiative energy source at the preselected wavelength, thespectral filter comprising a light absorbing agent, the light absorbingagent comprising a semiconductor material, the spectral filter furthercomprising an anti-reflection coating.
 70. An apparatus as defined inclaim 48, wherein the anti-reflection coating comprises a film ofsilicon dioxide or silicon nitride.
 71. An apparatus as defined in claim69, wherein the light absorbing agent comprises a semiconductormaterial, the semiconductor material comprising gallium arsenide,aluminum arsenide, silicon, germanium, indium phosphide or alloys there72. An apparatus for heat treating substrates comprising: a thermalprocessing chamber for receiving a substrate; a radiative energy sourcein communication with the thermal processing chamber for emittingradiant energy into the chamber; at least one radiation sensing devicein communication with the thermal processing chamber, the radiationsensing device being configured to sense radiation at a preselectedwavelength; a spectral filter being positioned in between the radiativeenergy source and the at least one radiation sensing device, thespectral filter being configured to absorb radiation being emitted bythe radiative energy source at the preselected wavelength, the spectralfilter comprising a light absorbing agent, the light absorbing agentcomprising a semiconductor material; and a cooling source for coolingthe spectral filter.
 73. An apparatus as defined in claim 72, whereinthe light absorbing agent comprises a semiconductor material, thesemiconductor material comprising gallium arsenide, aluminum arsenide,silicon, germanium, indium phosphide or alloys thereof.
 74. An apparatusas defined in claim 72, wherein the cooling source is configured tocirculate a cooling fluid adjacent the spectral filter.